1. Field of the Invention
The present invention relates to heavy-duty driveline master clutches of the type used in large vehicles such as trucks, tractor-trailers or the like and, more particularly, to a clutch brake for use with a driveline master clutch.
2. Description of the Related Art
The use and function of a clutch brake is well known in the art of vehicle driveline systems. A clutch brake is a device used to rapidly slow the rotational speed of a transmission input shaft when a driveline master clutch is disengaged to facilitate the shifting of gears in the transmission. Without a clutch brake, the time required to shift a transmission would be significantly increased, thereby complicating operation of the transmission in various driving modes.
A conventional clutch brake is a disc-shaped device, a portion of which is splined to the input shaft of the transmission and is activated by a master clutch release mechanism when the master clutch is disengaged. Upon disengagement of the master clutch, friction elements of the clutch brake are pressed between a transmission housing and the release mechanism to create frictional drag that slows the rotating transmission input shaft to facilitate gear shifting.
Normally, a release bearing, which is the operating portion of the release mechanism, moves between engaged (nearer the clutch) and disengaged (nearer the transmission) positions causing the master clutch to selectively connect and disconnect the transmission input shaft from the engine. When the release bearing is moved within a normal shifting range, the clutch brake is not engaged. However, when it is desired to rapidly slow rotation of the transmission input shaft to facilitate a gear shift, the release mechanism is moved beyond the normal shift range so as to trap and clamp the clutch brake between the release bearing and the transmission housing. When so moved, rotation of a splined brake disc is slowed or stopped and, consequently, the transmission input shaft is slowed or stopped.
In a “wear-through” style master clutch, the disengaged position of the release bearing is not consistently maintained over the life of the frictional components of the master clutch. Therefore, traditional clutch brakes that operate by engagement with a release bearing are not compatible with a “wear-through” style master clutch. Accordingly, there is a need for an improved clutch brake whose operation is not effected by engagement with a release bearing.